Catamaran offshore drilling vessel



Nov. 16, 1965 c. E. THoRNToN ETAL 3,217,581

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Nov. 16, 1965 c. E. THORNTON ETAL CATAMARAN OFFSHORE DRILLING VESSEL 13Sheets-Sheet 2 Filed July l0, 1965 IN VENTOR5.

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Nov. 16, 1965 c. E. THORNTON ETAL 3,217,681

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Nov. 16, 1965 c. E. THORNTON ETAL 3,217,681

CATAMARAN OFFSHORE DRILLING VESSEL Filed July 10, 1965 15 Sheets-Sheet 6INVENTORS.

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CATAMARAN OFFSHORE DRILLING VESSEL 13 Sheets-Sheet 8 Filed July l0, 1963650mg fav/PM W ATTORNEYJL Nov- 16, 1965 c. E. THORNTON ETAL 3,217,681

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Filed July lO, 1963 1965 c. E. THORNTON ETAL CATAMARAN OFFSHORE DRILLINGVESSEL 13 Sheets-Sheet 11 u; INVENTORS O m o charles E. Thomfon a GeorgeL. Temple ATTORNEYS Nov. 16,l 1965 c. E. THORNTON ETAL 3,217,683

CATAMARAN OFFSHORE DRILLING VESSEL 13 Sheets-Sheet l2 Filed July 10,1965 im .N m m s vom JN J N m g m m N oom om mwN U J w ho m rm m |.T Er- E IL. N ML 3 N Non oom e n a. m r EN om @om @om N \omN m Mw m @QN NonM D LT ma wll o n www Q \m.N ;mN .NN @I N N\ mmN\ v NN omN www@ mf my om/mwN NNN F @NN d NNN @QN J @N l NNNI m m @NNN E@ NN ATTORNEYS Nov. 16,1965 c. E. THORNTON ETAL 3,217,681

CATAMARAN OFFSHORE DRILLING VESSEL 13 Sheets-Sheet 13 Filed July lO,1965 INVENTORS Charles E. Thornon George 1 Temple ATTORNEYS UnitedStates Patent C) CATAMARAN FFSHORE DRILLING VESSEL Charles E. Thornton,Tulsa, Ukla., and George L. Temple, Houston, Tex., assignors to Reading& Bates Offshore Drilling Company, Tulsa, Okla., a corporation ofDelaware Filed July 10, 1963, Ser. No. 294,137 9 Claims. (Cl. 114-5)This application comprises a continuation-in-part of our applicationsentitled, Catamaran Type Olfshore Drilling Rig, Serial No. 153,592,iiled November 20, 1961, and Serial No. 195,440, filed May 17, 1962, nowboth abandoned.

This invention relates to a catamaran offshore drilling vessel and hasas its primary object the provision of an improved olshore drilling rigcharacterized by a pair of spaced hull means of catamaran type with adrilling platform and rig positioned thereon, the hull means beingsecured together or integral to insure greater stability of the rig andits associated parts.

An additional important object of the invention is the provision of anoffshore drilling rig which by the arrangement of its catamaran typehull means is readily adaptable to comparatively great depths of wateras Well as high wave conditions, to which conditions currently employedoffshore drilling rigs are unable to adapt.

As conducive to a clearer understanding of this invention, it may herebe pointed out that several methods of offshore drilling are currentlyemployed. Such methods include the use of drilling tenders tiedalongside a drilling platform erected offshore, with the actual rig fordrilling the well being located on a stationary platform, the legs ofwhich may extend many feet under the water and be sunk in the bottom.Another method employs the so-called self-elevating barge which is towedto the desired location and which is provided wit-h legs which are thenlowered to the iloor of the sea, the derrick and rig for drilling thewell being subsequently positioned on the barge platform, and the wellis drilled. At the conclusion of the drilling of such a well, if atender is employed the platform is either left in place for productionif a producing Well is achieved or dismantled if a dry hole results, andthe drilling tender is towed to another location. With respect to thebarge or self-elevating platform, in the case of a producing Well astationary platform is erected for production, and a selfelevationdrilling barge is towed to another location. Both of these methods arelimited by the depth of the water, and in many instances, by the waveaction at the particular location. Obviously, the erection of aplatform, or the use of a self-elevating barge as described is limitedby the depth of the Water. An important object of the invention is,therefore, the provision of a catamaran type offshore drilling rig whichmay be towed to the desired location, and suitably anchored, anddrilling conducted from the platform between the catamaran hull meansregardless of the depth of the water.

Applicants are also aware that some deep water drilling has beenachieved by means of barges, wherein the drilling unit and rig areoperated through an opening in the center of the barge. Under suchconditions the barge may be held in place when the water is too deep foranchors by outboard motors extended over both sides and operating atsuch speeds and power as may be necessary to hold the barge directlyover the drill pipe. An additional important object of the instantinvention is the provision of a means providing all of the advantages ofthe above-described method but providing an increased buoyancy factorand a relatively large deck area which is incompatible with theorganization of the barge having the center hole.

Applicants are also aware that drilling has been effected from a bargewhich is not anchored to a platform wherein the rig is extended over oneside of the barge and counterweights are provided at the water line onthe opposite side of the barge. An important object of the instantinvention is to overcome the difficulties of the last-mentionedarrangement by the provision of a catamaran type hull means wherein Itheincreased buoyancy factor is occasioned 4by the reduction of weightaiforded by the omission of the counterweight, as well as theelimination of much non-usable space in which drilling mud, fuel,supplies, etc., may be stored. In both of the lastmentioned types ofdrilling, the effective deck area is muchless than that achieved by theinstant invention.

The arrangement of the vessel with its two hull means separated to givea lwidespread, stable base provides superior behavior in waves duringdrilling operations, as Well as when riding out a storm or under tow. Toappreciate the features of the catamaran arrangement, consider first thepoor behavior and limited operating capacity if it were a single hulldrilling vessel. The conventional single hull means is notoriouslysensitive to rolling, particularly in wav-es that have a frequency closeto the natural frequency of roll of the ship. Under this condition,extremely large angles of roll can occur even with the wave approachingnearly head-on or stern-on, and even if the height of the wave is small.Therefore, it would be necessary to lay the vessel head-on or nearly soto the prevailing waves, which then requi-res that the derrick belocated near amidships in order to reduce ver- -tical movements due topitching. IDrilling could 'then be accomplished through a center well,which position minimizes roll as well as pitch but which limits drillingoperations to underwater completions, and presents difficulties ingetting on and off a well when the occasion requires. Drilling couldalso be accomplished from an over the side position which makes wellcompletion and positioning easier, but which then subjects the drillingrig to large rolling motions should waves arise from other than the headsea direction. Such is the case with ground swells, which may be longand ilat, heading in a different direction, from a storm area severalhundred miles away, and which can set up unexpected and severe Irolling.All in all, the sensitivity to rolling, the continual disturbance due topitching which must be abided in order to minimize rolling, thediscomfort and inefciency of the crew under these conditions, and thepossible high stresses occasioned in the derrick along with thediculties of handling drill pipe, make the use of a single hull drillingVessel unattractive and operationally uneconomical.

The catamaran arrangement provides a more stable working platform over awider range of conditions. Having great righting stability, the vesselwill not roll in its own period to large and dangerous angles, even instrong seas. At most, in long beam seas, it will roll to the slope ofthe waves, which seldom exceed 940 degrees even when at storm height. Inshorter Waves, the tendency of the widespread hull means to straddle thecrests or troughs of the waves reduces the roll angles to considerablylower values. The straddling characteristic also tends to reduce themotions and accelerations of heaving (the n'se and fall of the ship withthe wave). One generally unnoticed but important characteristic of thecatamaran is that, due to its tendency to follow the slope of the beamsea, its center of roll motion is well above the water line. Thus, inthe Vicinity of the drilling floor or slightly above, the roll motionsand accelerations should -be minimum. The single hull vessel, on theother hand, rolls at a center close to the water line, thus causingappreciable transverse motion and acceleration at any galassi fairheight above the water. The pitching characteristics of the catamaranvessel in head seas are essentially no different `from those of thesingle hull ship. However, due to the moderate roll behavior of thecatamaran there is no need to stay head-on to the waves duringoperation. In fact, it is the feature of being able to operate with aminimum of disturbance over a wide range of approaching wave directionsthat is probably the single most important characteristic of thecatamaran ship. When quatering to the sea, both roll and pitch motionsare present but both are at reduced intensity. Therefore, there shouldbe less need to reposition the vessel to suit a change in prevailing seadirection, and less chance of having to suspend operations in a strong,confused sea.

While the twin hull means must be spaced apart to provide the improvedstabiilty of the catamaran relationship, it is important that they notbe unduly separated since the great weight of the drill pipe and thetorque imparted by the rotary drilling table would pull the hull meansdownwardly and inwardly if an excessive separation were provided. It hasbeen found that to provide excellent stability characteristics whileprecluding undue strain on the vessel, the separation should be limitedto not in excess of the beam dimension of one of the hull means.

The greatly reduced motions under a wider range of sea conditionsall-ows the placement of the derrick in its most desired position-in aslot at the aft centerline of the vessel. This allows for greatest easein getting on and off, as well as for completing wells above water andsetting jackets. Also, in the event of a fire at the well head thevessel may readily be towed or self-propelled forward while fire boatsand other equipment is brought in to fight the fire. In contrast, if thefire were amidships, the entire drilling structure and vessel may bedestroyed, or at the very best, it would be necessary to break off thedrilling connection and perhaps lose the well. This would requireexcessive salvage costs `after the fire was eX- tinguished in moving'back over the drill pipe, replacing broken or damaged pipe, the wellfixtures and the like. Similarly, during a period of hurricane weather,a vessel having its drilling derrick at its stern, could move quicklyaway from the drilling operation, whereas in an amidship construction,the well head and the like must be severed causing the expenditure ofmuch time and money. Moreover, a stern mounted drilling derrickfacilitates folding or pivoting the same to lower the center of gravityand decrease the height of a vessel during transportation, while notaffecting the maneuverability of the same. Further, there is lesslikelihood of losing a well if a mooring cable should let go forward orto the side, since the vessel would tend to pivot about the well center.All of this means less risk in staying on location longer, both incontinuing to work in seas stronger than could be tolerated with asingle hull ship and in affording more time to make preparations to moveoff in the face of a severe storm.

In view of the type of operation for which the structures of the instantinvention have been designed, that is, an oil drilling operation,wherein the only buoyancy of the drill pipe is in that portion from thesurface of the water to the ocean fioor, perhaps two hundred to threehundred feet, with some eleven to thirteen thousand feet of pipe belowthe ocean floor, a great strain is presented to the vessel requiringextremely rigid and sturdy means connecting the twin hull means in orderto avoid damage to the same. The two hull means may be tied together bya series of rugged trusses at both ends of the ship, at the aft endforming part of the derrick substructure and .at the forward end, thehelicopter platform. Model test results, wherein the forces on the shipwere determined for extreme storm conditions, indicate that thecatamaran vessel will not be subject to racking or bending stresses thatwould 'be any more severe than those experienced by the same hull meansas single, individual vessels under the same conditions.

Alternately, and according to a further embodiment of the instantinvention, the catamaran offshore drilling rig may be integrally formed,the two hull means commun1- eating with, and forming part of, theconnecting structure, thereby increasing the strength and usable spaceof the vessel.

The catamaran offshore drilling vessel of this invention may either beself-propelled or towed, the former construction providing increasedmobility and flexibility m use.

Another very important object of this invention is the provision of acatamaran type -of drilling rig having a pivotally1 mounted derrick,which may be lowered during transport to permit the passage of the rigbeneath bridges, and also to lower the center of gravity of the rigduring towing or transport from one location to another when the rig isnot in use.

An additional object of the invention is the provision of a rig of thischaracter provided with an open deck area affording space for thelanding and take off of helicopters for transport of personnel andsupplies as may be necessary.

Additional objects reside in the combinations of elements, arrangementslof parts, and features of construction.

Still other objects will in part be obvious and in part be pointed outas the description of the invention proceeds and `shown in theaccompanying drawings wherein:

FIGURE 1 is a side elevational View of one form of catamaran typeoffshore drilling rig embodying the instant inventive concept;

FIGURE 2 is a top plan view of the rig of FIGURE 1, certain concealedportions thereof being indicated in dotted lines;

FIGURE 3 is a fragmentary schematic plan view of one form of layout ofspace in the deck house;

FIGURE 4 is a plan view of the main deck level;

FIGURE 5 is a view similar to FIGURE 4 of the hold;

FIGURE 6 is an enlarged sectional view taken substantially along theline 6-6 of FIGURE 2 as viewed in the direction indicated by the arrows;

FIGURE 7 is an enlarged sectional view ytaken substantially along theline 7 7 of FIGURE 6 as viewed in the direction indicated by the arrows;

FIGURE 8 is an enlarged sectional view taken substantially `along theline 8 8 of FIGURE 2 as viewed in the direction indicated by the arrows;

FIGURE 9 is an enlarged sectional view taken substantially along theline 9*9 of FIGURE 2 as viewed in the direction indicated by the arrows;

FIGURE l() is a front elevational View of the drill rig as shown inFIGURE l;

FIGURE 11 is a fragmentary side elevational view showing a modified formof drill rig construction and a portion of a modified form of hull meansto accommodate such rig;

FIGURE l2 is a fragmentary plan view of a modified form of constructionof the stern portion of FIGURE 2 embodying the derrick or drill rig ofFIGURE l1;

FIGURE 13 is a fragmentary view of a portion of one hull means similarto FIGURE 4 but showing a modified form of arrangements of components;

FIGURE 14 is a view similar to FIGURE 13 but showing a further modiedarrangement of hull components;

FIGURE 15 is a fragmentary diagrammatic plan View showing a modifiedform of the interior components of one of the hull means at the decklevel of FIGURE 4;

FIGURE 16 is a fragmentary plan view showing a modification of one ofthe hull compartments at the deck level of FIGURE 5;

FIGURE l7 is a similar fragmentary view showing `a modified arrangementof hull components at the deck level of FIGURE 5 at the bow of one ofthe hull means.

FIGURE 1s is a top pian View similar t0 FIGURE 2 but showing a modifiedform of construction whrein the drill rig is mounted amidships ratherthan at the stern of the vessel;

FIGURE 19 is an enlarged sectional view taken substantially along theline 19-19 of FIGURE 18 as viewed in the direction indicated by thearrows;

FIGURE 20 is an enlarged sectional View taken substantially along theline Ztl-20 of FIGURE 18 as viewed in the direction indicated by thearrows;

FIGURE 21 is an enlarged sectional view taken substantially along theline 21-21 of FIGURE 18 as viewed in the direction indicated by thearrows;

FIGURE 22 is a right or starboard side elevational view of a unitary,self-propelled embodiment of catamaran offshore drilling rig inaccordance with the instant inventive concept;

FIGURE 23 is a fragmentary top plan view of the helioport deck of theembodiment of FIGURE 22;

FIGURE 24 is a plan view of the drilling floor and upper deckarrangement;

FIGURE 25 is a plan view of the main deck level;

FIGURE 26 is a view similar to FIG. 25 of the second deck arrangementplan;

FIGURE 27 is a similar View of the third deck level;

FIGURE 28 is a plan View of the tank top and inner bottom arrangementplan; and

FIGURE 29 is a front or bow end elevational view with a portion of thedrilling rig broken away for illustrative convenience.

Similar reference characters refer to similar parts throughout theseveral views of the drawings.

Having reference now to the drawings in detail, particularly FIGS. 1 10,there is generally indicated at 30 a catamaran type of well drill rigwhich is comprised of a pair of hull means 31 and 32, which, in externalconfiguration, are substantially identical, although their interiorcomponents may be varied, as will be described more fully hereinafter.The hull means 31 and 32 are rigidly secured together so that they willact as a stabilizing platform for a drill rig derrick 33 and itsassociated mechanrsm.

In the form of the invention disclosed in` FIGURES 1 to lO, inclusive,the drill derrick 33 includes a lower reinforced tapered section 34which comprises a pair of divergentI legs, each of which is pivotallymounted as on a pivot 35 secured to a supporting member 36 carried by adrill platform 37. The drill platform 37 supports a drill operatingenclosure tains the usual winch for operating the drill line 39, whichextends through the usual pulleys 40 at the top of the derrick or drillrig 33. Rearwardly extending supporting braces t1 are pivotally securedas at 50 to the upper extremities of legs 34 and releasably secured asat 51 to platform 37, the arrangement being such that upon release ofthe connections 51 the drill derrick 33 may be tilted forwardly to lowerthe center of gravity of the catamaran 30 while in transport. A top deckstructure 52 supports a plurality of pipe racks 53 amidships and alsocarries a pair of deck houses 54, one of which is positioned on each ofhull means 31 and 32. Deck houses 54 in turn support angularly disposedfore and aft braces 55 and 56 as well as intermediate reinforcing braces57 which carry a fiat platform 58 extending across the two hulls in thespace therebetween to form a platform for the landing of helicopters ora helioport. 'I` he deck houses 54 may be internally arranged in anydesired manner, one illustrative form being disclosed in FIGURE 3wherein a plurality of cabins are provided, one of which 60 may comprisean office, another 61, the state room for the tool pusher or chiefdriller, a third 62, the masters quarters, a fourth 63, the hospital,and the other two 64 and 65 comprising spares or other cabins as may bedesired. Suitable heads and closet space 65 may be provided and locatedas desired, as may a ladder 66 leading or deck house 38 which con-` E tothe heliport platform or deck from the interior of the deck house 54 aswell as an external ladder 67.

Pipe racks 53 extend transversely over the main decks 70 of both hullmeans as well as the intervening space, and have intermediatelypositioned a catwalk 71 to provide access to any desired portion of theracks. Cranes 72 of conventional design and of any desired capacity,such for example, as 30 tons, are provided on opposite sides of the maindeck 70 and include the usual booms 75 and operating units 76. Cranes 72may be employed for any desired purpose, such as raising or lowering thedrill rig 33, or loading and unloading pipes from the piperacks 53.Ladders or external gangways 77 extend from the main decks upwardly tothe drill platform 37. Each hull may carry one or more lifeboats '78mounted on the usual davits 79 adjacent and exteriorly of the heliportplatform 58 on the outer side of the hull means. Such boats may compriselifeboats, or alternatively, merely gigs or tenders, as desired.

In this form of the invention, supply loading cranes or derricks 79 arepositioned adjacent the stern of each hull means and are rotatable forthe loading of supplies as may be necessary.

The main deck level 80 below the pipe rack or supporting deck isprovided with the usual rail 81 and doorways 82 leading into theinterior of the main deck superstructure underlying the pipe rack deck70 which deck contains the major operating equipment of the vessel. Inone illustrative embodiment of the invention, stern Winches 82 aremounted in angularly disposed relation on the aft portion of the maindeck level and carry anchoring cables 83 which extend at right angles toeach other, one directly rearwardly and the other directly outwardly ofthe hull. These winches and their associated cables in combination withsimilar Winches 84 mounted on the deck immediately above and theirassociated cables 85, which extend respectively directly out andforwardly of the bow, serve to hold the catamaran in a fixed positionfor drilling operations.

The interior arrangements of the main decks of hull means 31 and 32 maybe laid out in any desired manner, as, for example, the crews quarters87 may occupy the forward portion of each hull means, while immediatelyaft of the crews quarters in hull means 31 may be a generator room S8while hull means 32 in a similar location is provided with storage tanks89 for dry mud as well as pumping equipment. The pumping equipment isindicated at 90. Hull means 31 may also have water purifying and supplyequipment 91. Hull means 31 includes, in the illustrative embodimentshown, active mud pits 94, and an inspection well 95, as well as engines96. Hull means 32 may include a mud mixing pump 97, driving engines 98,and oil reservoirs 99. After the engine room there may be providedadditional quarters arranged in any desired manner as indicated at 100.

The hold, as best shown in FIGURE 5, may contain additional crewquarters as indicated at 101 as well as reservoirs for drilling water asat 102 and storage bins for reserve mud at 103. Immediately rearwardlyof the tanks 103, hull means 31 may be provided with a companion way 104while hull means 32 may be provided with a conveyor 105. Additionalmachinery 106 may also be provided, if necessary, while the compartmentsto the rear in each hull means contain bilge and ballast pumps 107, lirepumps 108 and fuel oil transfer pumps 109. The aft portion of each hullmeans may be provided with a stores locket 110 and a paint locker 111.Adjacent the bow drinking water may be stored in tanks 112 whilepressure sets may be stored in compartments 113.

It is to be understood that all these arrangements are optional andFIGURE 16, for example, shows a fragmentary rearrangement of thecompartment containing a ladder 104 wherein a storage compartment 115 isprovided and an additional conveyor 116 is positioned adjacent ladder104. In FIGURE 17, a modification of a bow compartment is shown whereinonly three tanks 112 are provided and a ladder 117 takes the place of afourth.

It will be readily understood that the arrangement of the deck planshereinbefore set out are to a large extent a matter of choice, and thoseherein shown are merely for the purposes of expediency.

The main deck level forward of the crews quarters may contain in onehull means the dining and recreation facilities 120, storage bins 121,and the galley 122. In the opposite hull means such space may be usedmerely for storage as indicated at 123.

FIGURES 13 and 14 disclose minor modifications of the rear portions ofhull vmeans 31 and 32 at the level of FIGURE 4. In this arrangement theWinches are arranged in perpendicular relation to the lines which theyserve, as indicated at 125 and 126 on both hu1l means. The lines 127corresponding to the lines 33 are thus subjected to a direct pull fromthe winch rather than run around pulleys as in the previously disclosedmodifications. In this modification, additional towing or mooring cables128 may be secured about suitable bights 129 or cleats secured to thedeck for towing or other purposes. Such an arrangement of the Wincheswill obviously require a reorganization of the interior compartment 100to the form indicated at 130. Such compartments may, obviously, beutilized for a wide variety of purposes. Similarly, FIGURE discloses agenerator assembly 131 adjacent the wall of the hull rather thancentrally as in FIGURE 4. y

The exterior of each hull means 31 and 32 is provided along its entirelength, and below the first; of a series of connecting trusses to behereinafter described with a plurality of tanks 135, which are suitablypartitioned, and which may contain, for example, tanks for the storageof fuel oil, as seen at 136, and drilling water as seen at 137 and washwater as shown at 133. Here again, the arrangement of the tanks islargely optional and, if desired, such tanks may be employed only forballast.

Means are provided for connecting the two hull means 31 and 32 inrelatively rigid relation, and may take var-ious structural forms. Forexample, FIGURE 6 discloses a relatively rigid beam 140 at the level ofthe main deck and above the tops of tanks 135, which is rigidly securedto each of the hulls 31 and 32. A second truss 141 may extend betweenthe hull means at the pipe rack deck level, while a third transversebeam 142 underlies the floor 58 of the heliport. Vertical beams 143 and144 extend centrally between beams 140, 141, and 142, wh-ile diagonalreinforcing braces 144 are provided between beams 142 141 together withsupplemental diagonal braces 145 extending between the center of beam141 and main connecting beam 140. The entire beam assembly andconnection is designated by the reference character 150, and any desirednumber of such assemblies may be provided. In the illustrativeembodiment herein shown, there are four of the 'assemblies 150, as bestshown in FIGURE 4, all of which may be substantially identical andconnected by longitudinally extending diagonal reinforcing bars orgirders 151. It is to be understood that various other bea-m supportarrangements may be provided as desired.

A pair of additional beam assemblies 155 are provided amidships, as`seen in FIGURES 2 and 7, and serve primarily to support the pipe racks40, although an auxiliary connecting function is performed by a lowerbeam 156 connected between the hulls 31 and 32 in substantial alignmentwith the beams 140. A top supporting beam 157 is also provided extendingdirectly beneath the pipe racks 40, While a vertical beam 158, diagonalbeams 159, serve further to support the central portion of the pipe rackdeck. While in the illustrative embodiment of the invention hereinshown, there are only two of these supporting members 155, it is to beunderstood that additional supports may be provided, if desired.

FIGURE 7 also discloses a support 160 having a flat top beam 161, andsuitable uprights 162 which serves as a support for the top of derrick33 when the latter is pivoted forwardly in the manner previouslydescribed. FIGURES 6 and 7 also disclose the fan housings 165 on thepipe rack deck level 7 0.

The aft portions of the hull means beneath the drilling platform 37 arealso connected by trusses or beams 166, from which diagonal beams 167extend upwardly to transverse supporting beams 168 which underlie thedrilling platform 37. Additional diagonally disposed truss beams 169extend from the main deck level 80 to the ends 171 of beams 163. Theabove-described beam assemblies are generally designated by thereference character 175, and in the illustrative embodiment shown, threeare provided immediately forward of the drilling well and connected bydiagonally extending members 176 similar to the members 151 previouslydescribed.

Additional supports are provided for the rear of drilling platform 37over the after well and between the sterns of the two hull means, and asshown in FIGURE 8, comprise beams which underlie supporting members 179for platform 137, and are in turn supported by diagonals 180 whichextend from the pipe rack deck level 70 of each of hulls 31 and 32upwardly. Deck houses 33 are also shown in FIGURE 8, and are providedwith additional diagonal reinforcing members 180 exteriorly thereof forfurther support of the drill rig platform 37.

1n this illustrative embodiment, the supporting structure is generallyindicated at 131, and, as shown in FIGURE 2, four of these may beprovided, or as many as may be necessary. It is to be understood thatthe particular construction of the connecting and supporting frameworksfor the heliport, the drilling platform, and the pipe racks, may all bevaried in accordance with the necessary stresses incident tothe propersupport of the components.

FIGURES ll and l2 disclose a slightly Imodified form. of constructionwherein the rig supporting platform is elongated as compared to theplatform 37 and the drill rig 186, although substantially identical tothe previous-ly described mast or rig 33, is supported further aft, thesupport taking the form of pivots 187 secured to supporting members 188mounted on the platform 185. The deck house 189 extends substantiallybeyond the stern of the hull means in contradistinction to thepreviously described deck house 33 carrying the usual drill rigcontrolling mechanism, and actually overhangs the stern, as does therearmost portion of platform 185. Reinforcing and support members 190correspond in function to the members 41 disclosed in the previousmodification with the exception that they are comprised of reinforcedgirder members and are secured to the rig at two points 191 and 192. Thelower ends of the members are pivotally mounted as on pivots 194 toupstanding supports 195 carried by the platform 135. In lowering the rig186 which is also provided with the usual upper pulleys 1% correspondingto the previously described mechanism 40, it is necessary to disconnectthe connections 191 and 192, whereupon the members 190 may be pivotallymoved about their pivot points 194 and the mast 186 lowered by means ofthe crane 72 as in the previously described modification. In this formof the invention, additional supporting members 181 may be utilized asmay be necessary. It may a-lso here be noted that the cranes 72 areemployed for the loading and unloading of pipe from the pipe racks, andfurther for the purpose of properly aligning the pipe beneath thederrick or drill rig fOr positioning in the Well beneath the surface asmay be necessary.

A modified form of construction is illustrated in FIG- URES 18 to 2l,inclusive, and is generally indicated at 200. In this embodiment thereare provided a pair of substantially identical hull means 201 and 202,each of which is provided with internal compartmentation, which may takea form similar or identical to the oompartmentation of the hulls of thepreviously discussed modification. The -two hull means in thismodification are connected by transversely extending girders or beams204 and 205 rigidly axed therebetween with the diagonally disposed beams9 206 reinforcing the construction, toward the forward part `of the hullmeans.

The hull means 201 and 202 may be provided on both sides with projectingwatertight pontoon type sections 207. Such sections may be employed toenhance the buoyancy of the vessel, or alternatively, may comprisestorage tanks as inthe previously described modification.

The fore part of the ship is provided with an upper deck 208 upon whichare mounted deck houses 209, which may contain oiiicers quarters or thelike, and which are bridged by a flat surface 210, the roofs of deckhouses 209 together with the surface 210 providing a heliport, generallyindicated at 213, and substantially similar to the heliport of thepreviously described modification. Longitudinally extending beams 214support the central section 210, as well as a lower central section 215,the eye beams 216 of which are supported by girders 217 supported by thediagonally disposed beams 206.

Fan houses 218 are provided at the rear of heliport 213 and the usualboats 219 supported by davits 220 are positioned on opposite sides ofthe heliport.

A pipe rack deck 221 extends substant-ially the full length of the shipand is provided with pipe supporting elements 222. Cranes 223 serve toload and unload as well as to position the pipes in the same manner asthe previously described cranes 72. The rear of the vessel is providedwith transverse hull connecting members 223 and 224, and the centralportion between the hull means is covered by a platform 225, the entirespace across the two hull means forming pipe supporting surfaces 226provided with pipe rack stops 227.

The various compartments 230 between the pipe rack deck 221 and the maindeck 231 are employed for the several purposes described in connectionwith the preceding modification, as are the similar compartments 232 inthe hold beneath main deck 231.

Any suitable interior arrangement of components is satisfactory.

In this modification, supporting members 205 and 204 and 223 and 224 areomitted from the center portion of this space between the two hull meansto provide a drilling Well beneath a drill rig supporting platform 235which is centrally positioned, and which supports a drill rig or derrick236 of conventional design. A deck house 237 on platform 235accommodates the drill rig controlling apparatus.

Platform 235 is supported on transverse girders 238 which in turn aresupported by upright beams 239 and reinforcing diagonals 240, whichlatter are secured to vertical uprights 241 supported by main deck 231.The arrangement is thus such that a secure and stable platform for thedrilling apparatus is provided, as well as a clear space through whichthe drill pipe may be extended.

As in the preceding modification, forward Winches 242 are connected toanchoring lines 243, while stern lines 244 are operated in a similarmanner from suitable winches 245 at the stern of each hull means. Theanchoring arrangement is substantially identical to that discussed inthe preceding modication.

Catwalks 246 extend substantially the full length of the pipe rack deckfore and aft of the drilling platform for the convenience of the crew,and suitable ladders 247 are provided at spaced intervals for accessbetween the various decks levels.

In this modification the drill rig 236 is stationary, and while itscentral location may enhance the stability of this arrangement when inanchored position, the construction of FIGURES 18 to 2l is obviouslymore unwieldy in transport and in towing.

Referring now to FIGURES 22 to 29, a self-propelled, unitaryconstruction, catamaran offshore drilling vessels is designatedgenerally by the reference numeral 250 and will be seen to comprise apair of spaced apart hull means 251 and 252 rigidly and unitarilysecured to each other by a connecting portion 253 formed integral withthe hull means 251 and 252 and extending from approximately the maindeck level down to the second deck level. Thus, this embodiment isconstructed originally as a catamaran rather than taking the hull meansof two former drilling tenders as in the embodiments describedhereinabove and assembling the same together in spaced apartrelationship by means of connecting trusses or the like such aconstruction allows for increased structural sturdiness and moreeiicient utilization of the deck and storage carrier.

The vessel 250 is provided with fore and aft deck houses 254 and 255,respectively, the roof of the former providing a helicopter landingsurface or heliport 256 and the roof of the latter providing a drillingfloor or deck 257 supporting a drill rig 258 which may be pivotally.

mounted as described hereinabove to lower the center of gravity duringtransportation, and a draw works shed 259 including the draw works 260.The arrangement of the upper deck may vary, but a convenient plan isshown in FIGURE 24 wherein the upper level of the deck house 254includes a rotary drilling table 260g, a pilot house 261, an oticc andcontrol rom 262 and a radio and chart room 263, while the lower level asseen in FIGURE 25 may contain the captains quarters 264, other quarters265, recreation rooms 266 and mess and galley rooms 267.

Handrails 268 and stairways 269 will be provided throughout the vesselas needed.

Rotatable supply loading cranes or derricks 270 are provided as arelifeboats and accompanying equipment 271 similar to previously describedembodiments.

Piperacks 272 extend transversely over the main deck 273 to supportpipes 274 for the drilling operation in a conventional manner. Also, aslope plate 275 and drag way 276 are provided between the piperacks 272.Conventional hatches are shown at 277, bulk material hatches at 278 andshell shaker and sand trap machinery at 279.

As seen in FIGURE 26, stern Winches 280 are mounted on the aft portionof the second deck level and carry anchoring cables 281 extending atright angles to each other, one directly rearwardly and the otherdirectly outwardly of each hull means 251 and 252. Similarly, bellWinches 282 carry anchoring cables 283 directed forwardly and outwardlyof the valve portion of each hull means 251 and 252. Personnel boatlandings 284 are provided on each side of the vessel 250. The seconddeck arrangement may include quarters 285 separated by passageways 286from spare or storage rooms 287, hospital areas 288, wash rooms andtoilets 289, freeze and chill rooms 290, engine rom 291, thaw room 292,laundry 293, change rooms 294, and dry stores 295. Large areas for sackmaterials storage may be provided at 296 and a halliburton unit at 297.Also, space for bulk cement bins and dry bulk mud bins is shown at 298and hatches at 299.

The third deck may have sea water ballast areas 300 fore and aft, spacedfor bow propeller machinery at 301, drill water storage at 302, washwater storage at 303, potable water storage at 304 and a distiller at305. The main switch board may be provided at 306, an upper machineryroom at 307, upper top rooms at 308, active and reserve mud areas at309, bulk mud bins at 310, bulk cement bins at 311, repair shops andspares storage at 312, a carbon dioxide rom at 313, and a gyro room at314.

The tank top and inner bottom arrangement plan shown in FIGURE 28 mayhave fuel oil storage 315, main and auxiliary generator units 316 and317, respectively, main mud pumps 318, a mixing pump 319, and thepropeller motors 320 to drive the propellers 321. Rudders 322 areprovided for steering the vessel 250.

It is to be understood that the arrangements shown for the unitary,self-propelled, embodiment of FIGURES 22 to 29 are merely exemplary andare set forth to illustrate the great working and storage area providedby such a construction. It will be readily seen that this unit is li llparticularly efficient and flexible in use providing a drilling rigwhich may be quickly moved from one location to another without a greatloss of operative time and which is self contained requiring noadditional equipment for propelling the vessel or for quartering the menand storing the machinery necessary to a drilling operation.

From the foregoing it will now be seen that there is herein provided animproved catamaran type offshore drill rig which accomplishes all theobjects of this invention including many advantages of great practicalutility and commercial importance.

As many embodiments may be made of this inventive concept, and as manymodifications may be made in the embodiment hereinbefore shown anddescribed, it is to be understood that all matter herein is to beinterpreted merely as illustrative, and not in a limiting sense.

We claim:

1. An offshore drilling vessel comprising a pair of substantiallyidentical hull means each having a bow portion, a stern portion, a beamdimension, a plurality of internal compartments to provide storagespace, machinery space and living quarters, and an upper surfacenormally disposed in a substantially horizontal plane, means includingparallel intermediate beams and a plurality of A-frames fore and aft ofthe intermediate beams all rigidly and structurally securing said hullmeans together in spaced catamaran relationship, a deck having an uppersurface in substantially the same horizontal plane as said upper surfaceof said hull means and extending transversely across the spacetherebetween, a drilling platform including an energized rotary drillingtable and drilling means operatively connected to said drilling tablefor conducting drilling from the platform at substantially thetransverse center of gravity of said drilling vessel between saidcatamaran hulls, regardless of the depth of the navigable water, saiddrilling platform being structurally supported by rearward supportbraces immediately above said upper surfaces of each stern of said hullmeans and extending transversely across the space therebetween, and anoil drilling derrick including hoisting line means for raising andlowering a drill string intermediate the aft portions of said hulls andxedly supported intermediate on said drilling platform operativelyinterconnected to said rotary drilling table and said drilling means.

2. A structure in accordance with claim 1l wherein said l2 hull meansare spaced apart a distance less than said beam dimension of one of saidhull means.

3. A structure in accordance with claim 1 wherein said drilling platformextends between said hull means adjacent said stern portions thereof.

4. A structure in accordance with claim 3 wherein said oil drillingderrick is pivotally mounted on said drilling platform, and means areprovided for raising and lowering said oil drilling derrick between avertical operating position and a horizontal transporting position.

S. A structure in accordance with claim 1 wherein pipe racks areprovided extending transversely over a major portion of said uppersurfaces of each of said hull means and over said deck.

6. A structure in accordance with claim 1 wherein said hull means areintegrally formed with said means securing the same in spaced catamaranrelationship.

7. A structure in accordance with claim Lxfurther including, incombination, means integral with saidvessel for propelling the same.

8. A structure in accordance with claim 1 further comprising, incombination, a plurality of bow and stern f anchor means at each hullmeans, and operating means for said anchor means.

9. A structure in accordance with claim 1 further comprising, incombination, a raised deck adjacent said bow portions of each of saidhull means extending transversely across the space therebetween andserving as a heliport.

References Cited by the Examiner OTHER REFERENCES .Tanes Fighting Ships,1959-1960, page 436, McGraw- Hill Book Co., New York.

MILTON' BUCHLER, Primary Examiner.

FERGUS S. MIDDLET ON, Examiner.

1. AN OFFSHORE DRILLING VESSEL COMPRISING A PAIR OF SUBSTANTIALLYIDENTICAL HULL MEANS EACH HAVING A BOW PORTION, A STERN PORTION, A BEAMDIMENSION, A PLURALITY OF INTERNAL COMPARTMENTS TO PROVIDE STORAGESPACE, MACHINERY SPACE AND LIVING QUARTERS, AND AN UPPER SURFACENORMALLY DISPOSED IN A SUBSTANTIALLY HORIZONTAL PLANE, MEANS INCLUDINGPARALLEL INTERMEDIATE BEAMS AND A PLURALITY OF A-FRAMES FORE AND AFT OFTHE INTERMEDIATE BEAMS ALL RIGIDLY AND STRUCTURALLY SECURING SAID HULLMEANS TOGETHER IN SPACED CATAMARAN RELATIONSHIP, A DECK HAVING AN UPPERSURFACE IN SUBSTANTIALLY THE SAME HORIZONTAL PLANE AS SAID UPPER SURFACEOF SAID HULL MEANS AND EXTENDING TRANSVERSELY ACROSS THE SPACETHEREBETWEEN, A DRILLING PLATFORM INCLUDING AN ENERGIZED ROTARY DRILLINGTABLE AND DRILLING MEANS OPERATIVELY CONNECTED TO SAID DRILLING TABLEFOR CONDUCTING DRILLING FROM THE PLATFORM AT SUBSTANTIALLY THETRANSVERSE CENTER OF GRAVITY OF SAID DRILLING VESSEL BETWEEN SAIDCATAMARAN HULLS, REGARDLESS OF THE DEPTH OF THE NAVIGABLE WATER, SAIDDRILLING PLATFORM BEING STRUCTURALLY SUPPORTED BY REARWARD SUPPORTBRACES IMMEDIATELY ABOVE SAID UPPER SURFACES OF EACH STERN OF SAID HULLMEANS AND EXTENDING TRANSVERSELY ACROSS THE SPACE THEREBETWEEN, AND ANOIL DRILLING DERRICK INCLUDING HOISTING LINE MEANS FOR RAISING ANDLOWERING A DRILL STRING INTERMEDIATE THE AFT PORTIONS OF SAID HULLS ANDFIXEDLY SUPPORTED INTERMEDIATE ON SAID DRILLING PLATFORM OPERATIVELYINTERCONNECTED TO SAID ROTARY DRILLING TABLE AND SAID DRILLING MEANS.